Apparatus for providing ducts between borehole wall and casing



Dec. 25, 1956 s. M. ZANDMER 2,775,3 4

APPARATUS FOR PROVIDING DUCTS BETWEEN BOREHOLE WALL AND CASING Filed May18, 1953 /Nl/fN TOR 5on5 Mme/v ZANDMER AT'T'GRNE Y.

United States Patent .0

APPARATUS FOR PROVIDING DUCTS BETWEEN BOREHOLE WALL AND CASING SolisMyron Zandmer, Calgary, Alberta, Canada Application May 18, 1953, SerialNo. 355,770

2 Claims. (Cl. 166-100) This invention relates to a novel apparatus forproviding ducts for the flow of fluids between selected earth strata andthe interior of a bore hole casing or liner.

Heretofore, bore hole casings have been set in drilled boreholes by acementing process in which fluidcement is forced down through the casingand then upwardly around the outside of the lower portion of the casingto fill the space between the outside of the casing and the surroundingearth. It has then been customary to perforate the casing and thesurrounding cement at the levels of producing strata by means ofhorizontal drilling or by means of gun-type perforators which fire aprojectile through the casing and cement to form passagewaystherethrough. Said known methods and apparatus have created variousdifficulties such as a shattering of the cement, destruction of thesealing bond between the casing or liner and the cement, and theformation of cracks in the cement making said cement subject todestructive attack by acids subsequently introduced to acidize andimprove the flow of fluids from productive strata.

A novel apparatus for establishing communication between producingstrata and the interior of a cemented bore hole casing or liner is shownin my joint application with one, Albert Joseph Jacobs, Serial No.285,201, filed April 30, 1952, nowPatent No. 2,707,997. Also shown in mycopending application Serial No. 294,251, filed June 18, 1952, nowpatent No. 2,708,000, is improved apparatus for so establishingcommunication between producing strata and the interior of a cementedbore hole casing or liner.

It is an object of this invention to provide an apparatus forestablishing communication between producing strata and the interior ofa sealed bore hole casing or liner.

It is another object of this invention to provide ducts betweenproducing strata and a bore hole casing or liner which do not damage inany manner the effectiveness of the seal between the casing or liner andthe surrounding earth formations.

it is a further object of this invention to avoid puncturing orperforating a casing or liner after it has been sealed and hence avoiddamaging the sealing material or the bond between the material and thebore hole casing or liner and/or the bond between the material and thebore hole wall.

It is a further object of this invention to provide a bore hole casingor liner with a plurality of laterial ductforming devices at variouslevels operable by pressure within the casing or liner to establish orposition the ducts between the casing or liner and different strata ofthe surrounding limestone formations without damaging the seal betweenthe casing or liner and the surrounding formation and between thevarious levels or strata.

It is a still further object of the invention to provide duct-formingdevices to be attached to a bore hole casing or liner adaptedeffectively to be moved outwardly by pressure to engage the wall of thebore hole and form cores between the casing or liner and the wall of thebore 2,775,304 Patented Dec. 25, 1956 'ice.

hole for a sealing material to be applied therebetween, parts of thedevices being made of a material which is dissolved in acid so that thecores may at least in part be removed to provide ducts or passagesaffording communication between the interior of the casing and the wallof the bore hole.

Other objects and advantages of this invention will become readilyapparent from the following detailed description of a preferredarrangement of apparatus and its method of use.

According to the invention, plungers movably supported in bushings fixedin holes through the casing are moved outwardly to engage the wall ofthe bore hole and provide cores surrounded by the sealing material whenapplied, and after the material has set, the cores are removed toprovide passages through the sealing material and the bushings, thusaffording communication between the wall of the bore hole and theinterior of the casing.

in the accompanying drawing forming a part hereof:

Figure 1 is a vertical section view partly cut away and partlydiagrammatic of a bore hole provided with a casing sealed in accordancewith this invention;

Figure 2 is a horizontal section view through the casing and through aduct-forming device, the device being shown in its initial position,before projection into engagement with a producing stratum;

Figure 3 is a view similar to Figure 2, on a reduced scale, but showingthe duct-forming device in its extended form; and

Figure 4 shows the duct-forming device in its final form, after partshave been dissolved to provide communication between the interior of thecasing and the wall of the bore-hole.

Referring now to the drawing, a bore hole 10 is drilled in the earth andlimestone by any conventional apparatus. In boring wells throughlimestone formations, for example, the bore hole may be approximatelynine inches in diameter and usually has a substantially smooth andregular surface.

A bore hole casing or liner 12 is positioned in the bore hole, and maybe formed of steel or aluminum tubing of about seven inches outsidediameter. This provides an annular space of about one inch acrossbetween the outer surface of the casing 12 and the wall of the borehole; the annular space is filled with a sealing material layer 13 whichis bonded to the wall of the bore hole and to the casing.

The sealing material comprises a suitable plastic, cement, or other suchmaterial as will not be dissolved by the acids used to acidize or treatthe well, or by the oil, gas, or other input materials used to increasethe productivity of oil or gas bearing strata.

For limestone, the acidizing agent currently used for increasedproductivity is hydrochloric acid. For the purpose of this invention,hydrochloric acid may be used for acidizing; and the sealing material 13may be a phenol resin type plastic such as is not attacked by the acid.

Earth formations usually have a plurality of oil or gas producing bandsor strata, indicated in the drawing by the numerals 11. Some of thestrata may be more porous than other adjacent strata. The porosity ofthe individual strata may be determined by analysis of specimen cores orby electrical testing apparatus, and the, permeability of each porousband of formation or stratum is expressed in terms of millidarcies.Where a bore hole traverses several strata of different porosities andpermeabilities, and the strata are to be treated by acids or otherchemicals, it is desirable that the seal 13 between various strata bemaintained unbroken so that upon application of acids under pressurethere will be no leakage outside of the casing 12 from one stratum 11 toanother, stratum of greater porosity or permeability. In actual practicethe strata may be found to be of small thickness and possibly spacedonly a few feet apart.

The section of well casing or liner 12 adjacent the strata 11 isprovided before its introduction into the bore hole with aplurality ofduct-forming devises mounted in thewall of thecasing 12 at levels tocorrespond with the indicated levels of the'strata 11 to be tapped.

One such duct-forming device will now be described first with referenceto its original position as shown in Figure 2. The device 15 comprises abushing 16 mounted in an opening in the casing 12 as by threads 1]. Theouter end of the bushing may be provided with recesses 18 to permitapplication of a spanner wrench to screw the bushing into the threadedopening of the casing 12. The bushing is such that, when applied, itdoes not project into the casing, but projects outwardly.

The bushing 16 is counter-bored as at 2 9 to define a shoulder or stop19 rearwardly of the forward end of the bushing. Threaded into thecounter-bore of the bushing is a tubular insert 21. The insert ispreferably made of two parts, 21A and 21B. The part 21A may be made ofsteel, and the part 2113 is made of a die-casting formed of pot metalcontaining zinc or of any other metal or substance easily dissolved byconventional acids used in acidizing, for example, hydrochloric acid.The part 21A of the insert is preferably locked to the bushing by asteel pin 34.

Slidable in the insert 21 is a member or plunger 22. The rearward end ofthe plunger is formed with an annular enlarged portion or shoulder 23.The plunger is in sealed sliding engagement with the bushing 16,forwardly of the shoulder 19, a conventional 0 ring seal 24 beingprovided for that purpose. The plunger 22 may be made of pot metalcontaining zinc or of any other metal or substance easily dissolved inthe conventional acid used. The plunger 22 is releasably held or lockedin the bushing 16 by shear pins 25. The pins are chosen to shear, andrelease the plunger 22 for outward movement, upon a predeterminedpressure being applied to the inner end of the plunger.

Means are provided to prevent movement of the plunger 22 rearwardly inthe bushing 16 after the shear pins 25 have been severed by pressure andthe plunger has been moved forwardly to engage the wall of the borehole. Thus, a wedging device is shown, comprising a plurality of balls26 held in engagement with a ramp 27 formed on the insert 21A, by asteel washer 28 urged toward the balls by a spring ring or Washer 29tensioned between the washer 28 and the shoulder 19. The arrangementis-such that the balls are always in contact with the ramp 27 and incontact with the plunger 22, so that the plunger is incapable ofmovement toward the casing 12 away from the wall of the bore hole 11,but is capable of movement outwardly from the casing 12.

A vent or bleed port 36 is provided through the insert 21, the ventopening at one end into the annular space between the insert 21 and theplunger 22. The outer end of the plunger 22 may be provided with a ring31 of resilient material, for instance rubber or Neoprene, adapted toengage the wall of the bore hole. Obviously, it is desirable that theouter end of the plunger 22 should engage the wall of the bore hole astightly or intimately as possible. The wall is not always smooth, evenif the hole is diamond-drilled, so that a resilient washer will bestserve to provide a good seal between the plunger and the wall of thebore hole. If the plunger 22 is hollow, as shown, a hole or passage 35is preferably provided at the inner end.

The plunger 22 is adapted to be moved by fluid pressure between itsinitial position within the casing 12, as shown in Figure 2, and itsextended position, in contact with the wall of the bore hole, as shownin Figure 3. The length of the plunger is so. chosen that its outer end,more particularly the rubber ring31, will engage the wall of the borehole before the shoulder or stop 23 engages the balls 26. Should thewall of the bore hole, facing the outer end of the plunger be notsmooth, that is, if it is locally recessed because of parts of theformation being chipped off, the efifective length of the plunger mightnot be sufficient to enable its to engage the wall of the bore hole whenfully moved outwardly. The presence of the shoulder 23, therefore, willprevent the plunger from being forced out of the bushing entirely.

The bottom of the casing 12 being closed by a releasable valve or plate29, a predetermined fluid pressure applied within the casing acts on theplungers 22 to sever the shear pins 25 and push the plungers outwardlytoward the wall of the bore hole to engage the same. The pressurerequired for this action depends on the shearing strength of the shearpins 25.

it is also possible that the plunger 22 may be made of a hard wax orsome other material which could be melted by heat or be easily dissolvedby oil or by acids.

The method of operation of the apparatus illustrated and described willnow be explained. The bore hole drilled in the limestone 11 is surveyedby conventional methods to determine both the porosity and permeabilityand actual level of the several porous strata 11 above the bottom of thehole 10. The casing 12 is then prepared with the duct-forming devices 15secured therein at the levels corresponding to the levels of the severalstrata to be tapped. The casing, with attached duct-forming devices, isthen lowered into the bore hole until it engages the bottom, presentingthe devices 15 to the several strata to be tapped. Fluid under pressureis then pumped into the casing until the pressure is sufiicient to causethe outward forces to shear the pins 25 and push the plungers 22outwardly so that they, more particularly the resilient rings 31,tightly engage the wall of the bore hole. The locking device, balls 26,prevents the plungers 22 from subsequent return movement back toward thecasing 12. Next, a sealing material, under a greater fluid pressure, isforced into the casing so as to open or force downwardly the releasablebottom closure 29 from its initial position, shown as 29a, to a positionbelow the lateral passages or ports 30 through the casing, the fluidsealing material then passing through the passages and upwardly, fillingthe annular space between the outer surface of the casing and the wallof the bore hole to the level required. The duct-forming devices 15 arethus surrounded by the sealing material and they thus provide cores orducts through the layer or wall of sealing material.

After the sealing material has finally set and has become bonded to theouter surface of the casing, to the wall of the bore hole, and to thebushing and to that part of the plunger 22 which projects out of thebushing, acid, such as hydrochloric acid, is pumped into the casing 12.The acid dissolves the plunger 22, and the part 21B of the insert, and apassage shown as in Figure 4 through both the bushing 16 and the layer13 of sealing material is formed, thereby alfording communicationbetween the inside of the casing 12 and the wall of the bore hole. As apossible alternative, an acid jet gun may be lowered opposite each bandof plungers 22 and acid sprayed on the plungers. If the plungers aremade of a hard wax, hot oil or other solvents may be spread against themto melt or dissolve the same.

It may be found possible to apply the sealing material before theplungers are moved outwardly to engage the wall of the bore hole, butthere appears to be no advantage to be gained by so doing; onlyexperience would show whether it would be possible, or desirable.

It is desirable to make the bushing 16 of steel rather than of potmetal, as steel is harder and is better able to withstand deformation orwear as when the casing is being lowered into the hole. Moreover, theeffective passage through the layer of the sealing material isdetermined by'theiuside diameter of the rubber ring, so that no usefulpurpose would be served by dissolving the bushing.

What I claim is:

1. In apparatus for use in a bore hole traversing a porous stratum to betapped, a duct-forming device adapted to be supported by a bore holecasing of smaller diameter than that of the bore hole to provide anannular space between said casing and the wall of the bore hole adaptedto receive a sealing material; said device comprising, an open-endedtubular bushing mountable in a hole through the wall of said casing, aplunger mounted in said bushing for outward movement to engage the wallof the bore hole to provide with said bushing a core to be surrounded bythe sealing material, means releasably locking said plunger againstoutward movement in said bushing, and means constraining said plunger toan outward movement, said plunger being of a material dissolvable inacid whereby said plunger may be dissolved to provide a passage betweenthe interior of said casing and the wall of the bore hole.

2. In apparatus for use in a bore hole traversing a porous stratum to betapped, a casing of smaller diameter than that of the bore hole toprovide an annular space between said casing and the wall of the borehole adapted to receive a sealing material, and a duct-forming devicesupported by said casing; said duct-forming device comprising, anopen-ended bushing mounted in a hole in the wall of said casing andprojecting outwardly therefrom, a

tubular insert in said bushing projecting into said casing and definingwith said bushing a bore, a plunger mounted in said bore for outwardmovement to engage the wall of the bore hole to provide with said bushing a core to be surrounded by the sealing material, means releasablylocking said plunger against outward movement, and means constrainingthe movement of said plunger to an outward movement, said plunger and atleast part of said insert being of a material dissolvable in acid, andsaid plunger when dissolved providing a passage afiording communicationbetween the interior of the casing and the wall of the bore hole.

References Cited in the file of this patent UNITED STATES PATENTS Re.23,393 Kurtz et al. July 24, 1951 2,033,562 Wells Mar. 10, 19362,186,349 Simmons Jan. 9, 1940 2,196,652 Baker Apr. 9, 1940 2,236,836Prutton Apr. 1, 1941 2,330,144 Powers Sept. 21, 1943 2,540,123 KinleyFeb. 6, 1951 2,546,669 Kirby Mar. 27, 1951 2,563,284 Seay Aug. 7, 19512,707,997 Zandmer et al May 10, 1955 2,708,000 Zandmer May 10, 1955

